The most important matter in medical treatment for diabetes is a blood sugar control. HbA1c (hemoglobin A1c, which is also called Glycohemoglobin) is one of indications of a blood sugar condition. HbA1c is the hemoglobin nonenzymatically combined with sugar. HbA1c is not influenced by a temporary change of blood sugar caused by meal and others. However, if a high blood sugar condition continues, the proportion of the combination rises, with the result that HbA1c becomes high. Thus, HbA1c is used as an indication of the blood sugar condition in one to two months prior to measurement, because the life of the hemoglobin is on the degree of 120 days.
Generally, a diabetic outpatient is subjected to a measurement of HbA1c in a visit to clinic of once a month, and whether the blood sugar condition is good or bad is evaluated in comparison with preceding measured values such as a measured value obtained in the latest month, etc. Based on the result of the evaluation, a policy of pharmacotherapy is discriminated, and/or a guidance for meal and exercise therapy is shown, in order to approach a normal value. Therefore, the diabetic has a very high interest in the change of HbA1c.
As a HbA1c measuring method, it is a general practice to sample blood in an medical institution and to perform a LA method (latex aggregation method) or a HPLC method (high-performance liquid chromatography method) by use of a clinical laboratory test apparatus. Incidentally, HbA1c may be measured in a medical examination, not only as an indication of the blood sugar condition but also for screening diabetes
In the meanwhile, it is also possible to directly measure a blood sugar value in order to confirm the blood sugar condition. It is general that after blood is sampled in the medical institution, the blood sugar value of the sampled blood is measured by the clinical laboratory test apparatus. On the other hand, by use of a simplified blood sugar measuring device, it is possible to measure in home with no assistance of a medical professional, and an insulin using person daily utilizes the simplified blood sugar measuring device.
As mentioned above, HbA1c is a very important item as the indication of the blood sugar condition, and is very highly interesting to medical professionals and patients. However, the measurement of HbA1c has to be carried out in the medical institution. On the other hand, since HbA1c is subjected to a strong influence of a daily blood sugar value, it might be possible to estimate HbA1c on the basis of a daily blood sugar measurement. However, an “in-day” change of the daily blood sugar value is very large because of influence of meal, and therefore, a frequent measurement is required. The simplified blood sugar measuring device might be utilized to measure the daily blood sugar value, but is not convenient to the frequent measurement, because of invasion by centesis and because of a measurement cost. Therefore, it does not become a measuring method for the HbA1c estimation.
As mentioned above, a diabetic is usually blood-sampled in the medical institution monthly or bi-monthly so that the blood sugar level, HbA1c and others are measured and, if necessary, the diabetic receives a life guidance. However, it is the most desirable to the diabetic if the diabetic can know a daily blood sugar condition so that the diabetic can control the meal in accordance with the known blood sugar condition.
In the meanwhile, in comparison with the blood sugar measurement, a urine sugar measurement can be relatively easily carried out because of its non-invasiveness. In addition, it is reported that since the urine sugar measurement dynamically reflects the change of the blood sugar value exceeding a sugar elimination renal threshold, it is possible to confirm and control a high level of postcibal blood sugar on the basis of the urine sugar measurement (Non-Patent Document 1). In a conventional urine sugar measurement, a qualitative analysis using a urine sugar inspection test paper was dominant. However, the Non-Patent Document 1 is reporting that as a biochemistry measuring instrument, a urine sugar measuring device has been used which makes a quantitative measurement possible in home. The urine sugar meter as the biochemistry measuring instrument is disclosed in for example Patent Document 1 and Patent Document 2.    Non-Patent Document 1: Journal of the Takasaki Medical Association, Vol. 55, Separate Volume, pp 75-79    Patent Document 1: JP-09-297120-A    Patent Document 2: JP-2006-153849-A    Non-Patent Document 2: “DIABETES”, Vol. 42, No. 11, 1999, pp 957-961    Non-Patent Document 3: “Diabetes Care”, Vol. 25, No. 2, 2002, pp 275-278    Non-Patent Document 4: “Diabetes Care”, Vol. 27, No. 2, 2004, pp 335-339
On the other hand, a correlation among the blood sugar value, HbA1c and the urine sugar value has been already researched (Non-Patent Document 2, Non-Patent Document 3 and Non-Patent Document 4). It is considered that if the blood sugar value rises up or falls down to become hyperglycemia in which the blood sugar value exceeds the sugar elimination renal threshold (which is generally considered to be 160 to 180 mg/dL although there is an individual difference), the urine sugar value will rise up or fall down as a matter of course. That is to say, if a risen or fallen urine sugar value continues for a considerable number of days, the blood sugar value should greatly rise up or fall down, with the result that HbA1c should correspondingly rise up or fall down after the considerable number of days. However, it is not possible to predicate how many days the risen or fallen urine sugar value is required to continue until any change appears in HbA1c, and what degree of magnitude is the actual change of HbA1c, because of a large individual difference between humans being. Similarly, because of the large individual difference, it is not possible to accurately convert a specific value α of the urine sugar value into a specific value β of the blood sugar value. In the prior art, accordingly, there is no method for knowing the blood sugar value from the urine sugar value.
From a different viewpoint, even if it can be said that if a risen or fallen urine sugar value continues for a considerable number of days, the HbA1c will certainly rise up or fall down, if a warning that “the blood sugar value rose” is given after the HbA1c has actually risen, it means that the diabetic has been resultantly left in a risen blood sugar condition for the considerable number of days, and the value of the warning is not so high. Rather than to know an accurate value of HbA1c just after the measurement of the urine sugar value, it is more important to diabetics to know whether the HbA1c is in an improving tendency or in a deteriorating tendency.
In addition, focusing to the urine sugar value per se, the measured value of the urine sugar value is an instantaneous value and has a large individual difference, and considering a specific individual, the urine sugar value greatly depends upon a condition of the same individual when the measurement was carried out. Therefore, although it is possible to know the instantaneous value of the urine sugar value, it is not possible to predicate whether the urine sugar value is in an improving tendency or in a deteriorating tendency, unless the instantaneous value takes an extreme value.